Development and maintenance of bovine cytotoxic lymphocytes with recombinant human interleukin-2

Long-term bovine lymphocyte cultures were initiated by stimulation with alloantigens and maintained in continuous culture using medium containing recombinant human interleukin-2 (rh IL-2). The development of specific and lectin-dependent killing was monitored following primary alloantigen challenge. Cytolytic activity was barely detectable after 7 days of culture, but gradually increased with peak activity occurring after 21 days of culture. A panel of monoclonal antibodies (MoAb) was used to determine whether a shift in the antigen phenotype of the cell population occurred during culture. The primary cell type that grew in culture was of the T-cell lineage with minimal or no expression of class II antigens. The activities of adenosine deaminase (ADA), purine nucleotide phosphorylase (PNP), adenosine kinase (AK), deoxyadenosine kinase (dAK), deoxycytidine kinase (dCK), 5'-nucleotidase (5'-N), AMP deaminase, hypoxanthine-guanine phosphoribosyl transferase (HGPRT or HPRT), and adenine phosphoribosyl transferase (APRT) were measured by microassay in resting peripheral blood lymphocytes (PBL) and in cells from long-term cultures. Large increases in the activities of PNP and HPRT with a decrease in the activity of ADA were observed. The data show that long-term cultures of lymphocytes can be readily generated, and that sequential changes in antigenic phenotype and function can be monitored and correlated with quantitative changes in enzyme activity.